1. Field of the Invention
The present invention relates to the field of agricultural machinery, and more specifically, to a piece of equipment that allows for the distribution of dry material over agricultural fields.
2. Description of the Related Art
Several different versions of a spraying system and/or tool bar have been invented and patented. None of these inventions, however, solves the problem of evenly distributing dry material over the surface of a large area with a piece of equipment that is easily maneuvered and transported. Furthermore, none of these inventions is designed to be used with existing air seeder carts, which are already present on most farms. The discussion below illustrates the evolution of the background art in this field.
In U.S. Pat. No. 2,657,949 (Morrison, 1953), the inventor disclosed an agricultural machine for distributing chemical weed destroyers and other spray materials. This invention is limited in that it contains spray nozzles for the distribution of liquid chemicals. It is also limited in that includes caster wheels, which can contribute to skidding and are also more difficult to maintain than non-caster wheels. Furthermore, with this design, the wheels on the outer ends of the spray boom are not aligned with the center section, which can also contribute to skidding.
In U.S. Pat. No. 3,447,750 (Weston, 1969), the inventor described a spraying boom for mounting on an agricultural tractor or similar self-propelled vehicle. As with the '949 patent, this patent is limited in that it is intended for use with liquid chemicals and not dry materials. In addition, this design encompasses a suspended boom, which is problematic in terms of efficacy and durability. The apparatus mounts on either side of the front of a tractor, so that it is pushed-not pulled-by the tractor.
In U.S. Pat. No. 4,117,892 (Dietrich, Sr. et al., 1978), the inventors provided an agricultural folding tool bar with a rigid cross frame. This invention is limited in that it includes a rigid (or double) cross frame as opposed to a single cross frame. Although it can be used to apply dry material, this device does so by means of a ground-engaging implement. It is intended more for use as a planter rather than as an applicator for dry fertilizer. This particular device does not have any center section, which would contribute to its stability, and it has non-aligned, caster wheels (i.e., the wheels are not aligned with the cross frame but rather sit behind it.
In U.S. Pat. No. 4,496,004 (Frase et al., 1985), the inventors described a collapsible farm implement that has a central support and two toolbars that are hingedly connected to the central support. One significant limitation of this invention is that it relies on hydraulics for its operation. Another limitation is that it is ground-engaging and cannot be used as a broadcasting system for distributing dry material on the surface of a field. This apparatus lacks the simplicity and ease of manufacture of the present invention.
In U.S. Pat. No. 4,709,857 (Wilger, 1987), the inventor disclosed an agricultural field sprayer frame with two laterally extending boom sections. The boom sections fold inward for transportation, but the folding and unfolding of the booms is controlled by hydraulics. As with the '949 and '750 patents discussed above, this invention is intended to be used for the distribution of liquid chemicals and not dry materials. This particular invention has a double hinge in the center of each boom that effectuates a double fold in the boom but that also contributes to the overall weakness of this design. The combination of a double tandem center section with four wheels on the booms increases the risk of skidding. 
U.S. Pat. No. 4,739,930 (Pask, 1988) involves an agricultural field sprayer with a main boom center section and wing sections that are hingedly attached to the center section. The wing sections are each comprised of two booms—a main boom and a spray boom. This invention is limited in that it applies only to the application of liquid chemical solutions. The invention is further limited in that it relies on hydraulics for movement of the booms. In addition, the wing sections are offset from direct alignment with the center section (in other words, this patent teaches away from direct alignment of the center section with the booms). The wing sections are supported by caster wheels that can be locked in a non-castering mode for transport.
In U.S. Pat. No. 5,029,757 (Bourgault et al., 1991), the inventors described a sprayer implement comprised of two wing booms that are independently controlled by hydraulic cylinders. This invention is limited in that it applies only to the spraying of liquid chemicals and it relies on hydraulics. It also has caster wheels, which can cause skidding when the tractor takes a sharp turn.
U.S. Pat. No. 5,117,579 (Tellefson, 1992) relates to a method and apparatus for applying fixed nitrogen to plants. The invention comprises a farming implement with a boom on which a series of bell-shaped members are mounted. Inside of each bell-shaped member is an ion emitter. An electrical circuit ion generating mechanism is connected to the ion emitters, and a power source is provided for energizing the electrical circuit. This invention is limited in that it is dependent upon the generation of electricity, and it cannot be used to broadcast dry material over a field surface.
In U.S. Pat. No. 5,178,328 (Broyhill, 1993), the inventor provided a spray boom apparatus that folds up vertically so that it can fit through a doorway. This invention is limited in that it is designed for use with liquid chemicals. In addition, the multiple folding points represent potential weak points in the structure.
In U.S. Pat. No. 5,673,854 (Kinder, 1997), the inventor disclosed a foldable spraying system with a closed boom (called a “bottomless box” in the patent) and four caster wheels. This invention is limited in that it applies only to the spraying of liquid chemicals.
U.S. Pat. No. 6,408,950 (Shoup, 2002) involves a foldable implement frame and hitch designed to carry an air-injection planter for corn and other hard kernel grains, rotary hoes, “duck-foot” field cultivators, and similar ground-engaging implements. The apparatus has two wing frames that are moved by a hydraulic motor. Motors are also used to move the field wheels and the dedicated transport wheels from ground-engaging, transport positions to stored positions. This invention is limited in that it applies primarily to ground-engaging implements and relies on hydraulics for its operation.
Lastly, U.S. Pat. No. 6,422,483 (Yocom et al., 2002) provides another spray boom apparatus. This device mounts on the front of the tractor and folds up both horizontally and vertically. This invention is limited in that it cannot be used to broadcast dry material over a field, and the multiple folding points contribute to the weakness of the overall structure.